In 2008, in a data set I have access to voters were given a choice between amnesty for illegal immigrants or the dramatic choice of deporting them (which I personally find too harsh).
Of those who had a view (most did) 59%-41%, the American public opposed amnesty for illegal immigrants. An identical 59-41% of voters wanted to build a fence on the border. Opposition to illegal immigration was larger in battleground states. This is a large chunk of voters for the republicans to go for.
What I have noticed in the Arizona debate is that the illegal immigration opinion is quite consistent. You get a 60-40% or 65-35% (of those who have an opinion) in most polls. This indicates that people have coherent and mature views on the subject, in contrast to many other issues (say, drilling for oil) where wording is central and where results are volatile.
Some people claim that while opposition for illegal immigration is wide, it is not deep, in contrast to support for amnesty (which the Hispanics care a lot about).
This claim is not true.
In 2008, a year with 2 wars and a weak economy, 15.3% of the public names immigration as the biggest problem facing the country. Of these, almost all (91%) opposed amnesty for illegal immigrants! The people most concerned with illegal immigration are very strongly opposed to amnesty.
Citizens who called immigration the biggest problem and who opposed
amnesty were much more likely to vote than average. Of those who actually voted in 2008, 16.7% were part of the strong anti-illegal immigration vote. (Remember that the pro-immigration Hispanics vote in 2008 was only 5.4% of the total vote and even less of the battleground vote).
Now, to be perfectly honest, Republicans cannot hope to win the presidency based on the strong anti-illegal immigration vote alone. The reason is that this group already voted for McCain-Palin in 2008. Of the voters who considered immigration the biggest problem and opposed illegal immigration, a whopping 91% believed the Republicans were best in handling the problem. Thus of the 16.7 about 14.9% went for McCain and 1.8% went for Obama (note that these are percentage points). But combine the strong anti-illegal immigration vote with the mild anti-illegal immigration vote, and they are half way there.
In the 2008 election, 59% of voters opposed amnesty, of which 16.7 percentage points stated at some point during 2008 (before the crash) that immigration was the biggest problem facing the country.
In the 2008 election, Obama got 52.9% of the popular vote. Of these, 19.5 percentage points (or more than one third) opposed amnesty for illegal immigrants. Of the 19.5 percentage points, 1.8 percentage point considered illegal immigration *the* biggest problem facing the country. For voters in the 18 battleground stats, this figure were 22.0 percentage points (over two fifth of Obama voters) who opposed amnesty and 2.2 percentage points who opposed amnesty and who consider immigration the biggest problem for the country.
In the 2008 election, the Democrats in the house got 53.2% of the vote. Of these, 20.7 percentage points (or close to two fifth) opposed amnesty for illegal immigrants. Of this 20.7 percentage points, 2.7 percentage points considered illegal immigration *the* biggest problem facing the country.
So of the 53% the Democrats got in 2008, when pro-amnesty Mccain was running, about 20% oppose amnesty, with 2-3% having very strong feelings about it. So something between 2 and 20 percentage points of the Democrat voters oppose amnesty and feel strong about it, and can potentially be peeled off. These are pretty big numbers in an otherwise evenly divided country.
Another huge chunk of the electorate are Republican voters who oppose illegal immigration, who can be turned to for money, votes and activism.
Lastly, this just shows the current support, not the latent support. The right have far from fully articulated the case against illegal immigration in the public debate, in which case the opposition will presumably rise even further.
Objective numbers rarely lie, and the numbers are telling us opposition to illegal immigration is deep and wide among the American voters, contrary to the impression the pro-illegal immigration media may be giving you.